Before the advent of flexible grid and supercarriers in optical networks, optical channels were assigned to a center frequency and fixed width (e.g., based on the ITU grid—195 THz, 50 GHz width). The flexible grid allows the assignment of an arbitrary amount of optical spectrum for channels (e.g., an arbitrary and flexible amount of spectrum). Supercarriers include a plurality of optical channels in a contiguous amount of spectrum with little or no guard bands between channels. For example, supercarriers can be routed in the optical network between the same ingress and egress points. The conventional fixed grid approach is simplistic from an Operations, Administration, Maintenance, and Provisioning (OAM&P) perspective, namely each optical channel can be managed by its channel assignment slot (i.e., center frequency+fixed width). With the drive to flex grid, supercarriers, and coherent modems, there is a need for a different approach.
Typically, electrical frames are mapped into one or more optical carriers, and the data model which is used to manage the underlying hardware is associated with the optical port, referred to as an Optical Channel (OCh). As described herein, a data model is used by a management system to perform OAM&P functions on underlying hardware. By associating the OCh with a physical port, a strong relationship is formed with the supporting optical carriers. For instance, a 100 G channel could be Quadrature Phase Shift Keying (QPSK) with a baud rate of about 35 Gbps or a 16-Quadrature Amplitude Modulation (QAM) with half the baud rate of the QPSK carrier. In the conventional approach, there was some base assumption between a physical port and the associated carrier (e.g., 10GE-LR4). However, as speeds increase on OCh, this relationship is harder to maintain.
Progress in high-speed electronics, especially in Digital-to-Analog Converters (DACs) and Analog-Digital Converters (ADCs), is allowing coherent optical modems to send symbol rates significantly higher than the 35 GBaud example above. One of the most popular and widely deployed realizations of the ITU fixed grid channel plan is the 50 GHz grid where channels are spaced by 50 GHz from each other. Optical filtering is required to perform functions like optical switching at Reconfigurable Optical Add/Drop Multiplexer (ROADM) sites and the like, which means that not all of the 50 GHz channel is usable by the optical signals. This results in a maximum practical symbol rate which can be supported by this channel plan which is less than 50 GBaud. Modems are currently being contemplated for these networks with symbol rates in excess of 50 GBaud and in the future higher symbol rates are expected to become practical. Therefore, the 50 GHz fixed grid is not sufficient going forward, nor is there a fixed grid which will efficiently accommodate all future generations of modems. The flexible grid allows for the allocation of the appropriate amount of spectrum for all applications with a minimum of loss of spectral efficiency.
With respect to supercarriers, logically these are considered a single unit from an OAM&P perspective. However, in practical network applications and with ever increasing speeds, it is expected the supercarrier will be decoupled and not maintain a convenient relationship with its associated underlying optical carriers.